Certain installations of the above kind, such as that described for example in U.S. Pat. No. 5,165,595, contain in a second memory operating laws or rules of the so-called "fuzzy" type, which enable the position of the distribution valves and mixing valve, and adjustment of the blower, to be managed on the basis of knowledge of the measured values of the inside temperature and outside temperature, the demand temperature, and a measured degree of exposure to the sun.
Because these installations have a large number of sensors, they are very complicated, and make it necessary to provide a large number of fuzzy rules, memorisation of which requires the use of high capacity memories: this in turn increases the cost of the installation. In addition, these fuzzy rules are generally dependent on each other, and this greatly reduces the speed with which the adjustments required for the various components of the installation by the control means can be defined. The rate at which the inside temperature converges towards the demand temperature is therefore also reduced, and this is detrimental to the comfort of the occupants of the cabin.
In addition, the fuzzy rules used in these prior art installations do not enable rapid decisions to be made when there is a sudden sharp change in the demand temperature or in the inside temperature.